Ski

ABSTRACT

A ski made of plastic or metal and has a core of highly flexible preferably fibrous material.

'U1iit1li-fSt ates Patnt xR v3102-3110110 Zeclniieister eta]. 1 July 16,1974 5 I 54 SK] 3,503,021 311910 Schmidt =1 111.115.... 250111-13 1. v 7 ......W.M.".W 1 1 Inventors 201mm Mumchwm 3.232.222 #131;- ififfii'n 1518023852? 1 am m' of 3,100,535 10/1912 McCoy =1 al. Mm/110x V Germany v 113 Assignee: Maser-mam r 5 v v AugshIrg-Numberg FOREIGN PATENTS 0R APPLICATIONS Akhaarsellschafl, Mumch, 1.351.207 12/1953 France m 280111-13 1' 5 Germany j 7 1,002,520 11/1954 Franoc..'....................... 280111.131. 1 .1221 101:0: 00022, 1971 [211 App]. No; 210,915 5 5- g 7 Primary Examiner-Kenneth H. B011 [3o] reign APPM P'hmy Dam Assistant Examiner-Milton L. Smith I Dec. 22. 1970 Gennany 2063167 Attorney, Agent, or Firm-Frederick W. Tpmbull '{521 us. a. urn/11.131, [511 1111. Cl. A630 5/12 [58] Field ofScarch-...280lll.l3 L, 11.13 R, 11.13 T, 57 ABSTRACT 280111.13 Y; 161/185, 170 1 0 1 Askimade of plastic or metal and hasacore of highly I {56] 0 References Cited YUNXTED STATES PATENTS 05,491,055 '1/1970 Talley ..200/31 flexible preferably fibrous material.

5 Claims, 6 Drawing Figures SKI In the past, laminated skis have been developed containing one or several core layers andlor an upper surface portion consisting of tough orgic or vegetable a high tensile strength interposed beneen the wooden layers or veneers. Said layer extemk over the whole length and width of the ski and is potioned close to the running surface, preferably on top of it.

The above constructions suffer from the disadvantage that the reinforcing elements hare great stiffness in the longitudinal direction but not in the transverse direction as required in modern skiing technique.

In the past it has been tried to construct a flexible ski with bar type steel reinforcing elemens in both tension zones extending longitudinally over the whole length, and in which two sets of steel inlays forming one ele-' ment and extending over the whole length of the ski serve as reinforcement, with the steel inlays of the first set running straight in a longitudinal E ection in known manner and those of the second set in a zig-zag pattern over the total length of the ski, thus alternately crossing the longitudinal reinforcement in pairs (German Patent Specification No. l,578,697). In this case, the steel inlays run in'tension channels" with acertain clearance within the ski and are guided laterally and secured at the ends of the ski. In view of the fact that the flexible wires serving as reinforcements must be run through several eyes and finally tensioned, d2 labor costs are considerable and cannot be reduced s'nce this design does not allow a mechanization of the production process. Furthermore, friction occurs between the highly resilient reinforcing wire and the lateral deflection points or profile edges. Thus, also in this case, the ski lacks from sufficient stiffness in the transverse direction since under normal conditions, i.e.when skiingon normal slopes, the longer steel elements of the zig-zag type reinforcement are not under ten 'un and can even be in a relaxed condition.

An object of this invention is to produce a ski combining the stiffness in the longitudinal fiection of conventional skis with a considerably grater stiffness in the transverse direction as compared to known designs. In other words. a ski is to be provided which is resistant to torsional forces, thus ensuring a high amount of grip. Moreover, it is intended to reduce the weight of the ski to a minimum.

In general, this object is obtained by using fibrous material for the reinforcing elements having a high specific stiffness (modulus of elasticity/specific weight ratio) which is wound about a core and cured after resin impregnation, or pre-treated and cured matted fibrous material with the threads wound at an angle of approximately 30 to 60', preferably 45, to the longitudinal axis of the ski in a criss-cross pattern over the width of the ski.

The advantage of this invention con ists in that the material properties (modulus of elasticity E, transverse stiffness G) of a fiber reinforced material of great specific stiffness and strength can be mixed by wrapping the threads at the proposedangle between approximatch} 30 to :60; preferably 4s', to the longitudinalaxis thus ensuring an amount of flexibility in the longitudinal direction comparable to known plastic and metal skis but a much-greater transverse stiffness.

It is found that a. reduction of the filament angle results in an increase in the modulus of elasticity (corresponding to the bending stiffness) and at the same time in a reduction of the t ansverse stiffness. With a filament angle of 30 (20') the transverse stiffness is reduced by about one-third (two-thirds) of the maximum value obtained at '45 In view of the fact that at greater filament angles, the stiffness shows an asymptotic characteristic, a limits: tion to an angle of approximately 60 seems to be necessary, all the more since at this angle the transverse stiffness is also reduced to approximately one third of it maximum. 1

A ski of the above design offers a transverse stiffness. never obtained before without requiring reinforcement ribs or similar features impairing. the flexibility and increasing the risk of failure.

An advantageous embodiment of this invention is the use of infinitely long, approximately 1 2 km, threads for the core with high specific stiffness and a thermal expansion coefficient approximately constant in the longitudinal direction, which are treated with resin, wrapped around a core member and then cured to form a flat hollow body positioned approximately in the neutral zone and extending over .the whole length and width of the ski. Said hollow core can be formed in the following manner: An infinitely long resin-impregnated strand of unidirectional fiber threads is wrapped about a core of constant section, e.g., a form-retaining metaf strip, preferably at an angle of 45 to the longitudinal axis; the side surfaces of the hollow body should form a maximum radius because of the high specific stiffness. Subsequently, the resin is cured at the minimum permissible temperature, in the case of epoxy resins and the metal strip is then removed from the hollow body at an extremely low temperature; this is possible because the radial dimensions of the core remain constant whereas the metal strip is subject to large shrinkage due to is great thermalexpansion coefficient.

'Another embodiment of this invention comprises a core of cellular material, e.g., polyurethane foam or a wooden core of-any desired section which can preferably be adaptedito the section of the ski. in this case, the core cannot removed after the wrapping operation.

According tothis-inventiomjthe resulting flat and laminated hollow body forms the reinforcing element of the ski which shows a great resistance to torsion, of

great transverse stiffness and allows easy control of the longitudinal stiffness by adjusting the height of the hollow body accordingly. Thus, the. characteristics of the ski can be variedfrom great flexibility as obtained by a core roughly corresponding to the sectional height of the ski. A significant advantage lies in the fact that both the ski of high flexibility and of low flexibility offers great transverse stiffness. Said hollow reinforcing core can advantagcously be positioned in the neutral zone of the ski since the stiffness is ensured by the configuration of the core.

in accordance withanother' feature of this invention, resin-impregnated matted fibrous material can be provided in one or seria pla'ri'es of the ski with the individual threads also positioned at an angle of to 60, preferably 45, to the longitudinal axis of the ski and in a criss-eross pattern.

'ln ;vi ew of the fact that the fibrous material is also commercially available in short length, this invention additionally provides the use of individual short filaments embedded in a resin matrix insteadof a hollow body or matted material.

' According tov this invention, carbon or boron-fibers are used;.an outstanding feature of said fibers is theirhigh specific modulus of elasticity or stiffness, i.e., the

-t'udinal aha.

flat hollow body 3{consisting of resin-impregnated carbon fibers, in wrapped about a core 4 of polyurethane and extending over thewwhole width and length of the ski. Shell 5 encapsulating the hollow body ratio between modulus of elasticity and specific weight p. These fibers are preferably embedded in synthetic resins in particular epoxy resin; Steel has a specific stiffness E/p 2,500 km, aluminium Elp 2,600 km,

and glass fibre reinforced plastic 60 percent glass) E/p 2,300 km, whereas, in the case of'carbon fiber rein forced plastic (60 percent C fibersYthe-means value of E/p --is approximately 13,000 km, which is comparable to'the specific stiffness of boron'fibres. The ratio between tensile strength 0' and specific weight p of than that of other known materials Moreover, reinforcing elements transverse and/or longitudinal direction of equal or dif resinreinforced by carbon. or boron fibersisalso higher consists of glass fibers reinforced resin and is bonded tothe core. A groove 6 is in the running surface.

FIG. 3 is a crossssectional view of the center portion. The height of the laminated hollow body corresponds to the sectional thickness of the ski as can also be seen from FIG.- 4, which is a cross-sectional view of the ski tail portion. The hollow body is again of extremely flat configuration.

it should be ham: that the height and width of the cross-sectional views shown do not reflect the actual dimensional relationship and that the waist of the ski has not been showm,-- FIG. 5 is a cross-sectional view of another embodiment of the ski according to this invention. In this case,

carbon fibers, embedded in a resin matrix 7a,-7b, 7e are re provided in the.

ferentfthickness where the thickness is selected according t'o'the desired flexibilityof the ski. In another embodirnent of this invention, on one-or on either side of the reinforcing elements of highspecific stiffness are used-in the longitudinal direction of the ski reinforcing elements of higher flexibility, preferably of glass fiber J reinforced plastic, forming the top and/or bottonsurface portion of the ski. This arrangement is advantageous'when the shell of the ski is to be of glass fiber re-; inforced plastic.

1 1-. 5 According to this invention, a skids obtained having great-transverse stiffness over its whole length, and in addition. its flexibility can be controlled as desired dur-' 7 ing manufacture by different filament angles and,

moreover, the ski of this invention-will retain its excellent-material properties over a longer period than 'skis' largely mechanized so that the customer can be ofi'ered a reasonable priced high-perfonnan'ceski even with higher material costs.

a'c'companing drawings, in which FlGg-l is a plan view of the ski, partly shown in sectioniifh FlC S .-'2, 3 and 4 are. respectivey *cross-sectional views-taken on the lines "-11. lllglll and lV-lV in FIG-.51: and

i-lGjLQSv is a cross-sectional n'ewthfrough a modificafl:

tion ofithe ski.

FlGL-fi is a cross-sectional view hrough a further modification of the ski. g As shown, a ski S has the top surface removed from its tail portion so that unidirectional carbon fibers l a criss-cross pattern at an angle a of to the ski longiof known design. The manufacturelof this ski can be .145 Themeans by which the objects of'this invention are obtained are described more fully reference to the v provided in three planes with two layers of polyurethane foam 8 in between. The side surfaces and the top and bottom surfaces}. and 9a consist of resin reinforced by glass fiber in the embodirne howmthe running edges are indicated by grooves'ltliand the running surface represented only by a line! 1; fe-two items'are bonded to the bottom surface fiortiom; t

As already indicated, this invention is not limited to the embodiments showmbut may include a-number of other embodiments which can also be a combination of the embodiments slibwn; "as an 'example,'the carbon fiber reinforced layers 7a,. 711,70 might be so connected at their side edges tliat an'-S-type section is formed or fibers reinforced' 'res'i Having now describedthemeans'by which the objects of this invention are obtained, j-

We claim: a

p l. A torsion-resis longitudinally elastic plastic ski having an elongated j nsertincluding fibers extending transversely to the lengthof the ski, said insert comprising a preimpregnated and hardened fiber compound the foam material tif-ll yersfi might be replaced by glass layers of fiber-reinforced plastic material whose strands extend at an angleoflfrom 30? to 60 transversely to the length of the ski, saidflayers' being connected along the edges of the insert adjacent the edges in such a way that they form an S in cross-section. A

2; The ski of c .l inwhieh short fibers are included in the layers;

' 3:. The ski as in claim 1 in which at least one side of the insert, less rigidi-striplike inserts, preferably of glass-fibenreinforcedplastic are placed in longitudinal direction ofthe.

4. The ski of clairrr3 in which the less rigid materials form the upper-and lower outer portions of the ski.

5. The ski of claim 1, in which cellular material is p0.- and 2 areivisible embedded in a layer-fof epoxy resin in 0', "sitioned betweenthe-layers of the insert. 

1. A torsion-resistant, longitudinally elastic plastic ski having an elongated insert including fibers extending transversely to the length of the ski, said insert comprising a preimpregnated and hardened fiber compound layers of fiberreinforced plastic material whose strands extend at an angle of from 30* to 60* transversely to the length of the ski, said layers being connected along the edges of the insert adjacent the edges in such a way that they form an S in cross-section.
 2. The ski of claim 1 in which short fibers are included in the layers.
 3. The ski as in claim 1 in which at least one side of the insert, less rigid, striplike inserts, preferably of glass-fiber-reinforced plastic are placed in longitudinal direction of the ski.
 4. The ski of claim 3 in which the less rigid materials form the upper and lower outer portions of the ski.
 5. The ski of claim 1, in which cellular material is positioned between the layers of the insert. 